Hemostasis: Control of Bleeding, Coagulation and Thrombosis, Animation · Alila Medical Media
讲解止血的三个阶段、血液凝固和血栓形成机制，适合练习医学相关词汇和理解生理过程。
Hemostasis is the process that controls bleeding at the site of injury.
止血是指在受伤部位控制出血的过程。
Blood loss is stopped by formation of blood clots that seal the breaks in blood vessels.
血液流失是通过形成血栓来阻止的；这些血栓能够封闭血管中的破裂部位。
Hemostatic mechanisms involve small cell fragments known as platelets and a dozen of soluble clotting factors.
止血机制涉及被称为血小板的小细胞碎片以及十几种可溶性的凝血因子。
These elements are always present in the blood in their inactive form, ready to activate, typically within seconds of an injury.
这些物质始终以非活性形式存在于血液中，一旦受伤，通常会在几秒钟内被激活。
When blood vessels are damaged, blood is exposed to components of the surrounding tissue.
当血管受损时，血液会接触到周围组织中的某些成分。
Some of these components bind to and activate platelets.
其中一些成分能够与血小板结合并激活它们。
Activated platelets are involved in all stages of hemostasis: - First, they secrete chemicals that induce blood vessels to constrict,
活化的血小板参与了止血过程的所有阶段：首先，它们会分泌化学物质，促使血管收缩；
thereby reducing blood loss.
从而减少了血液流失。
This is known as vascular spasm, the most immediate response to tissue injury.
这种现象被称为“血管痉挛”，是组织损伤后最立即出现的反应。
Vascular spasm is also triggered by local pain receptors, and by substances released by endothelial cells.
血管痉挛也是由局部疼痛感受器以及内皮细胞释放的物质所引发的。
– Second, activated platelets become adhesive to each other and to the endothelium; they clump together, forming a platelet plug.
其次，被激活的血小板会相互粘连，并与内皮细胞结合；它们聚集在一起，形成血小板栓。
They also secrete substances that attract other nearby platelets, activating them in a positive feedback loop, speeding up the formation and propagation of the plug.
它们还会分泌一些物质，这些物质能够吸引周围的其他血小板，从而在正反馈机制的作用下激活这些血小板，进而加速血栓的形成和扩散过程。
- Third, the surface of activated platelets serves as the site for coagulation - the formation of blood clots.
第三，活化血小板的表面是凝血过程（即血栓形成）发生的场所。
A clot is essentially a platelet plug reinforced with strands of a protein called fibrin - the final product of the coagulation cascade.
血栓本质上是由血小板形成的堵塞物，这种堵塞物还通过被称为“纤维蛋白”的蛋白质纤维得到加固；而“纤维蛋白”正是血液凝固过程中的最终产物。
Coagulation is a complex chain reaction where one clotting factor activates the next in the multi-step pathway.
凝血过程是一个复杂的连锁反应：在一个多步骤的路径中，某个凝血因子会激活下一个凝血因子。
There are 2 activation pathways for coagulation: - The extrinsic pathway starts with the exposure of blood clotting factors to the tissue factor,
凝血过程存在两条激活途径： - **外源性途径**：始于血液中的凝血因子与组织因子接触；
TF, in the extravascular tissue.
TF（转化因子）存在于血管外的组织中。
This pathway is induced by injuries to blood vessels.
这条通路是由血管损伤所诱发的。
- The intrinsic pathway, which involves only factors within blood vessels, is thought to serve as a positive feedback loop,
- 内在途径仅涉及血管内的相关因子，被认为是一种正反馈机制。
amplifying coagulation.
促进血液凝固的过程。
The 2 pathways converge into a common pathway producing thrombin and ultimately fibrin.
这两条代谢途径最终会汇聚成一条共同的代谢途径，该途径会生成凝血酶（thrombin），进而形成纤维蛋白（fibrin）。
Thrombin has the central role in the coagulation cascade.
凝血酶在凝血过程中起着核心作用。
It cleaves soluble fibrinogen to generate insoluble fibrin.
该物质能够分解可溶性的纤维蛋白原，从而生成不可溶性的纤维蛋白。
Thrombin also further activates platelets, and initiates a positive feedback loop that is essential for clot propagation.
凝血酶还能进一步激活血小板，并启动一个正反馈机制，这一机制对于血栓的形成至关重要。
Blood clots prevent blood loss during wound healing, but once the vessels are repaired, they must be dissolved to restore blood flow.
血栓在伤口愈合过程中可以防止血液流失，但一旦血管修复完成，这些血栓就必须被溶解，以恢复血液流动。
This process, called fibrinolysis, is a small cascade that produces the enzyme plasmin.
这一过程被称为“纤维蛋白溶解”（fibrinolysis），其实是一个小型级联反应，其最终产物是酶“纤溶酶”（plasmin）。
Plasmin cleaves fibrin and dissolves the clot.
纤溶酶能够分解纤维蛋白，从而溶解血栓。
Because most clotting factors are produced in the liver and their production requires vitamin-K, liver diseases such as cirrhosis,
由于大多数凝血因子是在肝脏中产生的，而其生成需要维生素K，因此像肝硬化这样的肝脏疾病会影响凝血因子的合成。
and vitamin-K deficiency may cause excessive bleeding.
维生素K缺乏可能导致出血过多。
The main bleeding disorders, however, are inherited.
然而，主要的出血性疾病都是遗传性的。
These conditions are caused by gene mutations that lead to deficiency of a certain clotting factor.
这些病症是由基因突变引起的，基因突变导致某种凝血因子缺乏。
They are usually treated with replacement therapy, using purified factors produced by recombinant technology, or frozen platelets.
这些疾病通常采用替代疗法进行治疗，具体方法包括使用通过重组技术生产的纯化因子，或使用冷冻血小板。
While formation of blood clots is critical to control bleeding, inappropriate coagulation can be dangerous.
虽然血栓的形成对于控制出血至关重要，但异常的凝血过程可能会带来危险。
In fact, far more people die from unwanted blood clotting than from clotting failure.
事实上，因不必要的血液凝结而死亡的人数远远多于因血液凝结功能障碍而死亡的人数。
Unwanted blood clot formation, known as thrombosis, is the most common cause of blocked arteries in heart attacks,
不必要的血栓形成（即血栓症）是导致心脏病发作时动脉堵塞的最常见原因。
strokes and pulmonary embolism.
中风和肺栓塞。
Factors that prevent inappropriate coagulation include: - Platelet-repellent property of the endothelium, - Anticoagulant factors - enzymes that prevent clot formation,
能够防止异常凝血的因素包括： - 内皮细胞的抗血小板作用； - 抗凝因子； - 阻止血栓形成的酶。
- and the fibrinolysis cascade that dissolves
- 以及能够溶解纤维蛋白的纤溶级联反应
blood clots after they are formed, Fluidity of normal blood flow also helps dilute the small amount of thrombin that forms spontaneously.
血栓形成后，正常血液流动的流动性也有助于稀释那些自发产生的少量凝血酶。
Decreased flow or stagnation of blood may increase risks for thrombosis.
血液流动减少或停滞可能会增加血栓形成的风险。